Which is the real problem: Overconsumption or overpopulation?

I would say that overpopulation is, because if it wasn;t for overpopulation then overconsumption wouldn't be a problem. If the population was halved then the amount of agricultural land/individal would double. The average amount of each fossil fuel per person would double. Also you have to remember that countries like Japan and England only produce about 60% of the food that they consume, so if the population in both these countries was halved then they would both be self sufficient with regards to food at least.